Two new studies presented at a gathering of U.S. cancer doctors and researchers this past weekend show therapeutic vaccines can be effective in fighting some forms of cancer. The vaccines target lymphoma and advanced melanoma. Researchers are excited by the progress they have made, but they say there is still much work to be done.

Researchers at the University of Texas M.D. Anderson Cancer Center, in Houston, say results from the two studies show great promise. The lymphoma vaccine extended the life of patients up to a year longer than patients who received a placebo and the vaccine may soon be approved by the U.S. Food and Drug Administration for clinical use.

The other study shows that a vaccine can be effective in fighting advanced melanoma, one of the most lethal forms of cancer. Researchers from Houston presented their findings on both studies over the weekend at the American Society of Clinical Oncology meeting in Orlando, Florida.

Doctor Patrick Hwu, Chair of M.D. Anderson's Department of Melanoma Medical Oncology, spoke to VOA by telephone about the melanoma vaccine study. "I think this is another step along the way that we are seeing some daylight with a cancer vaccine, inducing a big phase-three randomized study some benefit of the cancer vaccine compared to the control group," he said.

A phase-three study involves use of a control group so that comparisons can be made between those receiving the vaccine treatment with patients who do not receive the vaccine. A total of 185 patients at 21 cancer centers around the United States took part in the study. The patients who received the vaccine, along with the immunotherapy drug, Interleukin-2, had a response rate of 22.1 percent and a progression-free survival of 2.9 months, compared to 9.7 percent and 1.6 months for those who received only Interleukin-2.

Neither of the vaccines developed in these studies caused serious side effects. Both were designed to enlist the body's own immune system to fight cancerous tumors, a difficult task to accomplish since the immune system generally does not recognize cancer cells as foreign bodies.

Dr. Hwu says the melanoma vaccine works by using a synthetic chemical that mimics a protein found on the surface of the cancerous cells. The immune system attacks the foreign protein as well as the cancer when the procedure works. Dr. Hwu says even the modest success of such vaccines provides researchers with many more avenues for further study.

"These are among the first cancer vaccines that have been found to be positive, I think, but there is still a long ways to go. This is a work in progress and we have got to do a lot to make this better," he said.

The patients taking part in these studies had not been subjected to recent chemotherapy, which damages the immune system. Researchers believe some past vaccine studies may have failed because recent chemotherapy patients were admitted into the studies. Researchers say treatments that stimulate the patient's own immune system to fight cancerous growths could prove more effective at killing not only tumors, but small cancerous growths too small for doctors to detect.

In 2009, researchers project, more than 68,000 people will be diagnosed with melanoma and more than 8,000 of them will die. Around 65,000 people are diagnosed with non-Hodgkin's lymphoma every year.